The characteristics of an image may be subject to change as a result of various operations. Some of these operations may be initiated intentionally, such as, for example, a modification action carried out upon an image in order to impart certain desirable color characteristics to the image, while other operations may be non-color related operations that can unintentionally introduce undesirable distortions and color changes into the image.
A few examples of operations that are intentionally directed at modifying the color characteristics of an image include: changing the RGB ratio of a digital photograph based on a personal preference, changing the color intensity level in a projected color image so as to soften the colors for example, or changing a multicolored image into a sepia colored image. As can be understood, many of these modification actions are often based on individual preferences and perceptions, and are consequently, somewhat subjective in nature.
A few examples of non-color related operations that can undesirably modify the color characteristics of an image include: playing back a high-resolution movie in a video player having limited bandwidth capacity, propagating a video signal through a limited bandwidth transmission medium, using a codec having poor encoding/decoding characteristics, or carrying out illegal image transfer operations (such as making pirate copies of a movie).
While the non-color related operations described above are relatively easy to understand in terms of their impact upon an image, there are several other non-color related operations that cause a subtler and often overlooked impact on the characteristics of an image as well. A few examples of such operations include: cropping of an image, changing the aspect ratio of an image, and adding an object (such as a title) to an image.
These type of non-color related modification operations do not necessarily directly change the color characteristics of objects that existed in the image prior to the modification. However, the modification operations can lead to an overall change in image-related statistics. This change in image-related statistics may cause problems when image processing is subsequently carried out for purposes of rectifying color-related distortions in the image.
Thus, it is beneficial to consider color related operations, as well as non-color related operations, in a holistic manner for purposes of image processing.